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PubMed2006

Precompetitive anxiety and affective state of climbers in indoor climbing competition.

The purpose of this study was to measure the precompetitive anxiety and affective states of climbers, particularly with regard to sex and types of competition. 37 men (M=25.9, SD=3.8 yr.) and 10 women (M=25.9, SD=4.2 yr.), climbers who enrolled in Indoor Sport Climbing Competition, voluntarily participated in two different types of competition-speed and difficulty indoor climbing. The Competitive State Anxiety Inventory-2 and the Positive and Negative Affect Schedule were administered to all climbers just before the competition. The Sport Competition Anxiety Test was also administered to control competitive trait anxiety. Multivariate analysis of covariance yielded a significant interaction of sex and type of competition for affective state (Hotelling T2=0.21; F2,33=3.43, p<.05). Follow-up univariate analysis indicated that the mean Negative Affect score of women climbers before the difficulty competition was higher than mean Negative Affect scores of men before both speed and difficulty competitions and also the mean for women climbers before the speed competition (F1,34 = 6.15, p <.05). The results partially supported the hypothesis of differences in negative affect by sex and types of competition.

Adult↗
PubMed1988

Hospital behavior under competition and cost-containment policies. The California experience, 1980 to 1985.

Previous studies of hospital competition have found that greater competition leads to higher hospital costs. We describe herein the change in behavior of California's hospitals since the introduction of competitive and cost-containment programs. To examine the impact of California's pro-competition policies on hospital performance, we grouped the state's short-term hospitals according to the level of competition within their markets. From 1983 through 1985, total inpatient costs (inflation adjusted) increased by less than 1% in hospitals in low-competition markets compared with a decrease of 11.29% in hospitals located in highly competitive markets. After controlling for the effects of the Medicare prospective payment system program, the rate of increase in cost per discharge in hospitals in highly competitive markets was 3.53% lower than the rate of increase in hospitals in low-competition markets during the period from 1983 through 1985. We conclude that these pro-competition policies are having dramatic and potentially far-reaching effects on the nature of hospital competition, leading to increased competition based on price.

California↗
PubMed1996

Sperm competition games: external fertilization and "adaptive"' infertility.

We develop a model of a continuous fertilization process in which eggs and sperm are shed simultaneously, and in which the eggs are fertilized at a rate proportional to sperm density surrounding the egg mass. The model derives the ESS size and number of sperm in an ejaculate of an externally-fertilizing animal such as a fish species, in which the probability or intensity of sperm competition varies. It also predicts the ESS level of infertility (eggs remaining unfertilized after all sperm have died). Sperm size is assumed to increase sperm competitive ability (e.g. by increasing speed) and is also assumed to affect sperm longevity (either positively or negatively). Ejaculate expenditure is traded off against expenditure on obtaining further spawnings, and size and number of sperm can vary independently. The model predicts that the ESS ejaculate expenditure (product of sperm size and number) should increase, and that the ESS infertility should decrease with sperm competition intensity measured across species. Other results depend on the way that sperm size affects longevity. The available biological evidence suggests that longevity decreases with sperm size, probably because the main increase is in tail length which increases sperm energy expenditure. In this case, sperm size should increase with sperm competition intensity from an optimum at zero competition which maximizes the total distance travelled by the entire ejaculate in its lifetime, to an optimum for maximum sperm competition which maximizes the product of speed and sperm number. However, if longevity increases with sperm size, then the non-competitive optimal sperm size is greater than that for maximum competition, so that sperm size decreases with sperm competition intensity. Sperm numbers typically increase with sperm competition intensity, and always so if sperm competition is high enough, though decreases are possible over a range of low sperm competition intensity if (i) sperm longevity decreases with sperm size, and (ii) infertility is high enough.

Animals↗
PubMed1993

Sperm competition games: sperm size and sperm number under adult control.

Evolutionary games of sperm competition in which two males mate with the same female have previously considered sperm size to be fixed at some (small) constant level. Although male gametes in multicellular organisms are typically small compared with ova, they vary greatly both between and within groups, and sperm size sometimes correlates with the probability of sperm competition. This paper examines 'raffle principle' sperm competition games in which both size and number of gametes can be varied strategically under control of the diploid parent. If ejaculate investment trades off against the number of matings that a male can achieve, the evolutionary stable strategy (ESS) ejaculate expenditure (as a fraction of reproductive effort per mating) approximates to p/4 when the probability, p, of sperm competition is low. Sperm size may either: (i) increase a sperm's competitive weight (a measure of its advantage in the fertilization raffle), or (ii) influence its mortality rate in the female tract. On the simplest model, size is optimized after the marginal value theorem, and may be large or small depending on how size influences competitive weight or survivorship. Further, sperm size is independent of the risk of sperm competition, and only sperm numbers increase with this risk. However, some recent studies show sperm size to increase with sperm competition. The present analysis offers the following possibilities: (i) there are unidentified constraints on sperm number, so that ejaculate mass can increase only by increase in sperm size; (ii) competitive benefits of size become more important as sperm numbers increase; (iii) size mainly increases survivorship, and sperm competition risk increases with the mean duration between mating and fertilization; and (iv) size increases competitive ability at the expense of survivorship, and sperm competition risk decreases with time between mating and fertilization. These conclusions relate to advantages conferred by size on sperm before fertilization; they do not affect the prediction of previous models that no component of sperm size should evolve for provisioning the zygote.

Animals↗
PubMed1997

Dizocilpine-like discriminative stimulus effects of competitive NMDA receptor antagonists in mice.

Several non-competitive NMDA receptor ion channel blockers, competitive NMDA antagonists and compounds acting at other sites on the NMDA receptor complex were examined for their ability to substitute for the discriminative stimulus effects of dizocilpine. Swiss-Webster mice were trained with food to discriminate the non-competitive NMDA receptor antagonist, dizocilpine (0.17 mg/kg), from saline in a T-maze. Mice rapidly acquired the discrimination with minimal amounts of drugs required for training and testing. Several non-competitive antagonists dose-dependently substituted for dizocilpine with a rank order of potency of dizocilpine > TCP > (-)-MK-801 > SKF 10,047 > dextrorphan > PCP. There was a positive correlation between the potencies of the compounds that substituted for dizocilpine and their previously reported affinities for the [3H]dizocilpine binding site of the NMDA receptor ion channel. Compounds acting at other sites on the NMDA receptor complex, including NMDA, the partial agonist at the strychnine-insensitive glycine site, ACPC, and the polyamine antagonist, ifenprodil, failed to substitute fully. In addition, the AMPA antagonist, NBQX, the monoamine uptake inhibitor, cocaine, and the GABAA receptor agonists, diazepam and phenobarbital, failed to substitute fully for dizocilpine. However, like the ion channel blockers, the competitive NMDA antagonists, CGS 19755, NPC 17742, (+/-)CPP and LY 233536 dose-dependently substituted for dizocilpine. The competitive antagonist, LY 274614, and its active enantiomer, LY 235959, failed to substitute for dizocilpine, each producing severe disruptions in locomotor activity. That most of the competitive antagonists substituted for dizocilpine is in accordance with other behavioral data (e.g., ataxia, locomotor activity) documenting similarities in the effects of non-competitive and competitive antagonists. These findings are also consistent with results of clinical investigations suggesting overlap in the behavioral and subjective profiles of competitive and non-competitive NMDA blockers.

Animals↗
PubMed1999

Competition for antigenic sites during T cell proliferation: a mathematical interpretation of in vitro data.

By fitting different mathematical T cell proliferation functions to in vitro T cell proliferation data, we studied T cell competition for stimulatory signals. In our lymphocyte proliferation assays both the antigen (Ag) availability and the concentration of T cells were varied. We show that proliferation functions involving T cell competition describe the data significantly better than classical proliferation functions without competition, thus providing direct evidence for T cell competition in vitro. Our mathematical approach allowed us to study the nature of T cell competition by comparing different proliferation functions involving (i) direct inhibitory T-T interactions, (ii) Ag-specific resource competition, or (iii) resource competition for nonspecific factors such as growth factors, and access to the surface of Ag-presenting cells (APCs). We show that resource competition is an essential ingredient of T cell proliferation. To discriminate between Ag-specific and nonspecific resource competition, the Ag availability was varied in two manners. In a first approach we varied the concentration of APCs, displaying equal ligand densities; in a second approach we varied the Ag density on the surface of the APCs, while keeping the APC concentration constant. We found that both resource competition functions described the data equally well when the Ag availability was increased by adding APCs. When the APC concentration was kept constant, the nonspecific resource competition function yielded the best description of the data. Our interpretation is that T cells were competing for "antigenic sites" on the APCs.

Algorithms↗
PubMed1998

Are men more competitive than women?

This study uses competition diaries to see whether women and men differ in (a) what they compete over, (b) whom they compete with, and (c) their competitive tactics, including use of aggression. In Study 1, university students kept diaries of their competitive interactions during the term. Sex differences, few overall, were as follows: (a) men's diaries contained more same-sex competition, (b) women competed more about looking attractive whereas men competed more about sports, and (c) men used physical (but not verbal) aggression more frequently than women. In Study 2 strength of competition was also measured by questionnaire. Women and men felt equally competitive overall, but men felt more competitive about athletics and sexual attention whereas women felt more competitive about looking attractive. In men, but not women, competitiveness for financial success was correlated with various aspects of mating competition. Young men were more competitive than older men in a variety of domains and were also more physically and verbally aggressive, but no age difference in aggression was found for women.

Adult↗
PubMed2000

Competitiveness and conflict behavior in simulation of a social dilemma.

This experiment examined the competitive behavior in a seven-choice Prisoner's Dilemma game of 108 adult students (68 women, 40 men) classified as high, average, or low in competitiveness based on their scores on the Competitiveness Index. Participants were then presented one of three preprogrammed response conditions representing (1) Competitive, (2) De-escalating, or (3) Noncompetitive conflict behavior from a simulated opponent. Participants high in competitiveness engaged in more competitive behavior and reported higher satisfaction with the task than those low in competitiveness. As expected, the Competitive conditions elicited more competitive behavior than Noncompetitive conditions. The results suggest competitive individuals may be particularly susceptible to social cues that trigger competitive behavior.

Adult↗
PubMed2003

The effect of HMO competition on gatekeeping, usual source of care, and evaluations of physician thoroughness.

OBJECTIVES: To examine the effects of HMO enrollment and HMO competition on evaluations of physician thoroughness through their effects on gatekeeping and having a usual source of care and to determine whether the effects of HMO competition spill over to individuals not enrolled in HMOs and whether these effects differ in those enrolled vs not enrolled in HMOs. STUDY SAMPLE: A nationally representative sample of 27 441 adults from the household component of the Community Tracking Study-Round 1 (July, 1996, through July, 1997). STUDY DESIGN: A retrospective econometric analysis of Community Tracking Study data merged with measures of HMO competition. METHODS: Gatekeeping was regressed on HMO enrollment, HMO competition, and control variables using ordered logistic regression. Usual source of care was regressed on gatekeeping, HMO enrollment, HMO competition, and control variables using logistic regression. Evaluation of physician thoroughness was regressed on gatekeeping, usual source of care, HMO enrollment, HMO competition, and control variables using multivariate regression. RESULTS: HMO competition increases use of gatekeeping and gatekeeping increases having a usual source of care for all individuals. For HMO enrollees, HMO competition increases having a usual source of care, whereas for those not in HMOs, it decreases having a usual source of care. For all individuals, having a usual source of care increases evaluation of physician thoroughness. For those in HMOs, gatekeeping decreases evaluation of physician thoroughness. CONCLUSIONS: For HMO enrollees, the overall effect of HMO competition is to increase evaluations of physician thoroughness. For those not in HMOs, although there are HMO competition spillover effects, they are offsetting, resulting in no overall effect of HMO competition on evaluations of physician thoroughness.

Adolescent↗
PubMed1982

Competition theory, evolution, and the concept of an ecological niche.

This article examines some of the main tenets of competition theory in light of the theory of evolution and the concept of an ecological niche. The principle of competitive exclusion and the related assumption that communities exist at competitive equilibrium - fundamental parts of many competition theories and models - may be violated if non-equilibrium conditions exist in natural communities or are incorporated into competition models. Furthermore, these two basic tenets of competition theory are not compatible with the theory of evolution. Variation in ecologically significant environmental factors and non-equilibrium in population numbers should occur in most natural communities, and such changes have important effects on community relations, niche overlap, and the evolution of ecosystems. Ecologists should view competition as a process occurring within a complex dynamic system, and should be wary of theoretical positions built upon simple laboratory experiments or simplistic mathematical models. In considering the relationship between niche overlap and competition, niche overlap should not be taken as a sufficient condition for competition; many factors may prevent or diminish competition between population with similar resource utilization patterns. The typically opposing forces of intraspecific and interspecific competition need to be simultaneously considered, for it is the balance between them that in large part determines niche boundaries.

Animals↗
PubMed2004

Subjective functional assessments and the return to competitive sport after anterior cruciate ligament reconstruction.

OBJECTIVES: To examine (a) return to competitive sport within 12 months of anterior cruciate ligament (ACL) reconstruction, (b) maintenance of competitive participation at follow up, and (c) the relation of the level of sports activity and competitive participation at follow up to subjective functional assessments. Also to address the incidence of continued competitive participation despite notable functional problems with the operated knee at 12 months and follow up. METHODS: All patients were competitive athletes before injury and had undergone ACL reconstruction by the transtibial endoscopic technique with either a bone-patellar tendon-bone or a multiple looped hamstring autograft. Evaluation was carried out a mean of 43 months (range 24-73) after surgery by a postal questionnaire in which the Cincinnati sports activity scale (CSAS) and Cincinnati sports function scales were presented in conjunction with closed questions on change in competitive level and the presence of complaints. RESULTS: Of 109 selected patients, 77 (71%) responded. At follow up, 62 of 77 patients (81%) reported that they had returned to competition within 12 months of surgery. Within the same time frame, 55 of the above 62 patients (89%) also claimed to have returned to the level at which they were competing before injury (or higher). At follow up, 30 of the above 55 patients (54%) reported to still be competing at this high level. Twelve of the above 55 patients (22%) also admitted to major problems with the operated knee at that time. The overall incidence of patients competing despite major functional impairment in the operated knee was 13 of 62 (21%) at 12 months and six of 47 (13%) at follow up. Thirty eight patients (49%) were active in sport at least four times a week at follow up (CSAS level 1), and, using Spearman's rank correlation between CSAS scores and total sports function scores, r was calculated to be 0.44. Competitive and male patients had higher total sports function scores at follow up than non-competitive (p = 0.005) and female (p = 0.02) patients respectively. CONCLUSIONS: The reported return to competition at the previous level, both within 12 months and at follow up, was high but as expected considering the standard of treatment, patient selection, and study exclusion criteria. Patients with few functional complaints maintained a high level of sporting activity, even after discontinuing competitive participation.

Anterior Cruciate Ligament↗
PubMed2005

Hemodynamic and autonomic changes induced by Ironman: prediction of competition time by blood pressure variability.

We hypothesized that the extreme endurance exercise of an Ironman competition would lead to long-standing hemodynamic and autonomic changes. We investigated also the possibility of predicting competition performance from baseline hemodynamic and autonomic parameters. We have investigated 27 male athletes before competition, 1 h after, and then for the following week after the competition. The Task Force monitor was used to measure beat-to-beat hemodynamic and autonomic parameters during supine rest and active standing. Heart rate (P < 0.001) was increased, and stroke index (P = 0.011), systolic blood pressure (P = 0.004), diastolic blood pressure (P < 0.001), total peripheral resistance index (P < 0.001), and baroreceptor reflex sensitivity (P < 0.001) were decreased after the competition. The 0.05- to 0.17-Hz band of heart rate and blood pressure variability was increased (P < 0.001 and P < 0.001, respectively), the 0.17- to 0.40-Hz band of heart rate interval variability was decreased after the competition (P < 0.001). All parameters returned to baseline values 3 days after the competition. After the competition, the autonomic response to orthostasis was significantly impaired. The 0.05- to 0.17-Hz band of diastolic blood pressure variability before competition and weekly net exercise training, but not the other hemodynamic and autonomic parameters, were related to competition time in multivariate regression analysis (multiple r = 0.70, P < 0.001). The marked hemodynamic and autonomic changes after an ultraendurance race, which are compatible with myocardial depression in the face of sympathetic activation and reduction of afterload, return to baseline after only 1-3 days. Because the 0.05- to 0.17-Hz band of diastolic blood pressure variability contributes to the prediction of competition time, the analysis of blood pressure variability in the frequency domain deserves further study for the prediction of endurance capacity.

Adaptation, Physiological↗
PubMed1995

Seasonal variation in fitness parameters in competitive athletes.

In many sports, training for successful competition has become virtually a year-round endeavour. To assist in better preparation, a competitor's year may be divided into phases such as off-season and in-season, indicating reduced or increased competition commitments, respectively. A number of studies have described the effects of seasons or periods of competition, training, detraining and reduced training on aspects of physical fitness. Depending on performance level, the type of sport and the fitness parameter in question, the swings in fitness variables reported may be as high as 18% from one season to another. In elite competitors, anaerobic parameters, heart frequencies, subcutaneous fat, flexibility and haemoglobin levels remain relatively unchanged throughout the year. Aerobic metabolism and muscular strength may demonstrate noticeable (mostly unfavourable) changes, and plasma hormonal levels normally follow changes in training intensities. Aspects related to long term fatigue and genetics, and to appropriate training are just a few explanations for these observations. It is still not known whether greater fitness gains attainable with longer off-season training programmes can be successfully maintained over the duration of the competition season. However, the consensus would seem to be that specialised training (based on technique and competition tactics only) is inadequate for fitness maintenance and/or improvements. This is perhaps supported by the general trends found in the literature regarding muscular strength: while supervised off-season conditioning programmes may result in significant improvements for both recreational and competitive athletes, no such changes are normally observed after competition seasons. These findings may reflect, amongst other factors, a lack of optimal training intensity to bring about strength increases during in-season periods. In novices and in athletes at low competitive levels, training seasons may lead to considerable functional improvements of the cardiorespiratory system, coupled with occasional increases in muscular strength and decreases in body fat. Relatively low fitness levels at the beginning of training have been put forward as an explanation for these improvements. Seasons of training and competition result in no significant changes in flexibility measurements. Similar changes to those found in novices and in athletes at low competitive levels may also be seen in children and adolescents engaged in sport, although their fitness improvements are consistent with normal patterns of growth and development. No differences have been identified between male and female athletes participating at different competition levels.

Adolescent↗
PubMed2005

Effect of plant density on competitiveness of Brassica napus, Sinapis alba and S. arvensis under water stress conditions.

Under Mediterranean climate, oilseed rape is subjected especially to the competition of weeds with respect to water. Herbicides registered for this crop do not effectively control species of the same family, in particular Sinapis alba and Sinapis arvensis. Moreover, there are no results of the effect of plant density on the competitiveness of these species. The purpose of this experiment was to determine if the competitiveness of the species varies according to the total density. The experiment was carried out in pots under greenhouse conditions, according to a replacement series method. Plant densities tested were 2, 4 and 8 plants per pot. The results of the replacement series diagram and those of relative crowding coefficients showed that Brassica napus was the most competitive, whatever the density is. This classification is explained primarily by leaf area. Indeed, the intraspecific competition due to B. napus has affected more its leaf area than the interspecific competition. Conversely, the intraspecific competition due to S. arvensis has less affected its leaf area than the interspecific competition. Regarding S. alba, the intraspecific competition effect was less severe than the interspecific competition effect due to B. napus and more severe than the interspecific competition effect due to S. arvensis on S. alba

Brassica napus↗
PubMed2006

[Quantitative relationships of intra- and interspecific competition in Cryptocarya concinna].

The monsoon evergreen broad-leaved forest (MEBF) in Dinghushan Nature Reserve (DNR) has been considered as a zonal vegetation in lower subtropical China, with a history of more than 400 years. In this paper, the intra- and interspecific competition intensity in Cryptocarya concinna, one of the constructive species in MEBF in DNR was quantitatively analyzed by Hegyi single-tree competition index model. The results showed that the intraspecific competition intensity in C. concinna decreased gradually with increasing tree diameter. For C. concinna, its intraspecific competition was weaker than its interspecific competition with Aporosa yunnanensis. The competition intensity of interspecific competition with C. concinna followed the order of A. yunnanensis > Schima superba > Gironniera subaequalis > Acmena acuminatissima > Castanopsis chinensis > Syzygium rehderianum > Pygeum topengii > Blastus cochinchinensis > Sarcosperma laurinum > Pterospermum lanceaefolium > Cryptocarya chinensis. The relationship of the DBH of objective tree and the competition intensity between competitive tree and objective tree in the whole forest and C. concinna population nearly conformed to power function, while that between other competitive tree and the objective C. concinna tree conformed to logarithm function. There was a significantly negative correlation between the competition intensity and the DBH of objective tree.

China↗
PubMed2006

Changes of pituitary, adrenal and gonadal hormones during competition among female soccer players.

AIM: This study was intended to investigate various hormones during competition among female athletes. METHODS: Subjects were elite female soccer players (n=9). Blood samples and profiles of mood states (POMS) were obtained before (Pre), during 3 days of competition (Competition), and after competition (Post-3 days). Serum concentrations were determined for dehydroepiandrosterone sulfate (DHEAS), cortisol (C), prolactin (PRL), testosterone (T), adrenocorticotropic hormone (ACTH), luteinising hormone (LH), and follicle stimulating hormone (FSH). RESULTS: Levels of C and PRL increased significantly during competition (2nd: P<0.05; 3rd: P<0.01) compared with Pre. Levels of LH increased significantly during competition (3rd day) compared with Pre (P<0.05). Levels of DHEAS changed significantly during competition, whereas levels of T, ACTH, and FSH were unchanged during competition. The fatigue score of POMS increased significantly during competition (2nd day) compared with Pre (P<0.05). CONCLUSIONS: We demonstrated that competitive stress affected hormonal status in female athletes. These findings suggest that hormonal changes reflect physical and mental stress during competition.

Adrenal Cortex Hormones↗
PubMed1987

Comparison of three worksite weight-loss competitions.

Competition is an effective means of promoting weight loss in worksite programs. This study was designed to determine the most effective structure of competition through a comparison of two kinds of competition within one worksite. Two competitions were between teams and one was among individuals. While all three competitions produced significant weight loss and lower attrition than previous worksite programs, the team competitions produced significantly lower attrition rates and significantly greater weight loss than the individual competition. Patterns of loss over time and the distribution of losses for groups also differed, with a smaller proportion of successful participants in the individual competition. The results suggest that team support as well as competition is a necessary component of effective worksite weight loss competitions.

Adult↗
PubMed2005

Experimentally increased social competition compromises humoral immune responses in house finches.

Although social behavior can substantially influence an individual's physiology, few studies have examined whether intraspecific competition compromises individual immunocompetence. We experimentally manipulated the intensity of social competition in captive non-breeding house finches (Carpodacus mexicanus) by supplying few (high competition) or many (low competition) feeding sites. We tested whether elevated levels of social competition caused individual changes in aggression rates, humoral immunity, body mass, and baseline and stress-induced corticosterone concentrations. We also examined whether physiological responses to social competition were related to an individual's social status. We found that house finches under high social competition had significantly higher aggression rates, lower antibody responses, and lost more body mass. Within flocks, dominant individuals mounted stronger immune responses in both competition treatments. Our statistical power to detect differences in circulating corticosterone concentrations was low, but we did not find any support for the hypothesis that corticosterone concentrations mediate immunosuppression among or within flocks: baseline and stress-induced corticosterone concentrations did not differ under high and low social competition, were unrelated to individual social status, and did not predict the extent of immunosuppression among individuals. Overall, we documented that two universal components of social behavior, intraspecific competition and social status, modulated the strength of a humoral immune response in house finches.

Adaptation, Physiological↗